The present invention relates to a facsimile apparatus, copier or similar image forming apparatus including a reading section for reading a document in the form of a sheet with stationary optics while conveying the document. Also, the present invention relates to a document reading device applicable to, e.g., a facsimile apparatus or a copier for reading a document or sheet with stationary optics while conveying the document.
An image forming apparatus having an apparatus body and one or more system units connected thereto is conventional. The system units are commonly connectable to different types of image forming apparatuses and thereby promote cost saving. It is therefore preferable with an image forming apparatus to simplify the functions of the apparatus body, so that sections which can be separated from the apparatus body can be implemented as system units.
It is a common practice with a facsimile apparatus or similar image forming apparatus including a reading section to mount an ADF (Automatic Document Feeder) in order to promote the efficient handling of a stack of documents. Basically, the ADF feeds one document from its tray or stacking section to a transport path while separating it from the underlying documents. The transport path extends linearly from the document feed side to a document discharge side. A contact line image sensor or similar stationary optics is located at a preselected position on the transport path, and reads the document being conveyed along the transport path. A relatively thick document not feasible for the above separation and feed mechanism is directly inserted to the reading section by hand, and then automatically conveyed. The linear transport path, however, has a substantial length and renders the entire apparatus bulky. To save space, there has been proposed and put to practical use a turn-over type sheet-through ADF capable of discharging a document read by stationary optics in the direction of sheet feed, as taught in Japanese Patent Publication No. 63-40514 by way of example. This kind of ADF has a document separating and feeding section for feeding one document while separating it from the others, a generally U-shaped turn-over path, and a transport path having a reading position assigned to stationary reading optics and for conveying the document turned over by the turn-over path.
Assume that an image forming apparatus has its document reading section, document conveying section along which a document fed from a stacking section is conveyed, and fixing unit for fixing a toner image on a sheet constructed into independent units, and that such units are individually connectable to the apparatus body. This brings about a drawback that the space available in the apparatus body cannot be efficiently used by the units, increasing the overall size of the apparatus body. Particularly, to read both sides of a document while conveying it only once, the document conveying unit must turn over the document and again feed it to the reading position, or two reading sections must be located at both sides of the transport path. This kind of arrangement increases the space to be allocated to the conveying unit or the spaces to be allocated to the reading units, making it difficult to miniaturize the apparatus.
The conventional turn-over type sheet-through ADF has the following problems. To switch the direction of document transport, the ADF usually includes a generally U-shaped turn-over path having an extremely small radius of curvature. Therefore, the turn-over path cannot deal with a relatively thick document or a relatively long document. Specifically, when a document is conveyed along the turn-over path, an extremely great conveying force is necessary (usually, the conveying force is substantially proportional to the width of a document and proportional to the square of the thickness of a document). Therefore, the turn-over path does not allow rollers to convey a broad and thick document therethrough alone. Further, a long document is apt to bring about a loop jam when conveyed through the turn-over path. It follows that the kind of documents which can be dealt with by the above ADF is limited.